Now, as wireless local area networks (Wireless Local, referred to as WLAN) have been widely used for data communication, WLAN network loads are constantly increasing. With the increase in the number of users, the efficiency of the WLAN network exhibits an apparent lowering trend. Simply increasing the rate cannot solve this problem. As an alternative technology to address the network efficiency, multi-user parallel transmission has attracted wide attention and research. In the related art, the multi-user parallel transmission technologies include multi-user Multiple Input Multiple Output (MU-MIMO) technology (Spatial Domain Multiple Access), Orthogonal Frequency Division Multiple Access (OFDMA) technology (Frequency Domain Multiple Access) and so on.
In a WLAN, an access point (AP) and a plurality of non-AP stations (non-AP STAs) associated with the AP form a basic service set (BSS), as shown in FIG. 1. The multi-user parallel transmission in a WLAN generally means that the plurality of non-AP STAs transmit data to the AP simultaneously, referred to as uplink multi-user (UL MU) transmission, or the AP transmits data to the plurality of non-AP STAs simultaneously, referred to as downlink multi-user (DL MU) transmission. A typical uplink-downlink multi-user transmission frame exchange sequence is as shown in FIG. 2.
In an existing solution, the AP is required to trigger a UL MU transmission. For example, the AP may send a trigger frame to trigger, or the AP may trigger by a radio frame carrying a trigger information field in the radio frame. The trigger frame or the radio frame carrying a trigger information field carries scheduling information of the station, such as identification information of the station, time for uplink transmission of the station, frequency resource information, time-frequency offset calibration information of the station, the package length of uplink transmission of the station, and so on. After the AP sends the trigger frame or the radio frame carrying a trigger information field, the station receives the trigger frame or the radio frame carrying a trigger information field. If the identification information of a station is carried in the trigger frame or the radio frame, it means that the station is scheduled in this UL MU transmission. If the station has data to be transmitted, the station may get prepared, and may get synchronized according to the time-frequency offset calibration information instructed by the AP, and transmit the data at the allocated time and frequency resource.
In the related art, data transmission modes of a WLAN system with Quality of Service (QoS) may be classified into competitive transmission and non-competitive transmission. The competitive transmission mechanism refers to an enhanced distributed channel access mechanism (EDCA). That is, the service stream data has a priority attribute, each data packet of the service stream is mapped to one of 4 Access Category (AC) queues, waiting for transmission according to the priority. Each AC has a set of competitive parameters. The competitive parameters include arbitration interframe space (AIFS), maximum duration for occupying channel and transmission, Contention Window max (CWmax) and Contention Window minimum CWmin Different AC competitive parameters may take different values, and may have different AC priorities. The non-competitive transmission mechanism refers to HCF controlled channel access (HCCA). The data packet of the service stream transmitted through the non-competitive transmission mechanism does not actively compete for a channel, but sends the data packet to the AP after the station receives a polling frame sent from the AP.
The transmission of the 4 ACs is performed competitively. Specifically, the competing process is that for each AC, a station sets up an initial value of a CW window as CWmin, selects an integer randomly between [0, CWmin], and sets a Backoff timer with the value. Then, the station monitors a channel, when the channel idle time period satisfies the AIFS of the AC, the station performs a random backoff. Each time the station monitors an idle time slot, the Backoff timer decreases by 1. When the Backoff timer reaches 0, the AC acquires a transmission opportunity and transmits data. When the transmission collision occurs, CW increases exponentially and the final value of CW does not exceed CWmax. When the transmission is performed successfully, the value of CW is reset to CWmin A control frame and a management frame are not data frames, and in the related art, it is generally prescribed that the control frame and the management frame are transmitted through a particular AC.
In the related art, the trigger frame may be transmitted at a predetermined transmission time instant, or may be transmitted in a competitive manner. For example, the station may be instructed to report their respective length of the AC buffer queue. After the AP side acquires the buffer data length of the AC queue from the station side, the uplink AC queue also participates in the competition at the AP side. If an uplink AC completes successfully, the trigger frame of the AC queue is sent to trigger UL MU transmission.
However, the related art does not have a solution as how to set the CW value and the Backoff timer of the uplink AC queue at the station side and the AP side, after a trigger frame is sent in a competitive manner, and the station performs UL MU transmission according to the instruction of the trigger frame.
No effective solution has been proposed yet as to how to set the CW value and the Backoff timer of the uplink AC queue at the station side and the AP side, after a trigger frame is sent in a competitive manner in the related art.
This section provides background information related to the present disclosure which is not necessarily prior art.